You can also add a background to your re-combination.

Creating a File node to add as a background to your re-combination

1. In the Hypershade, select Maya > 2D Textures > File to create a File node. In the File node Attribute Editor, click the Browse button beside the Image Name attribute to navigate to your background image file.
2. Select Maya > Other Textures > Layered Texture to create a second Layered Texture.
3. Add layeredTexture1 as a layer to layeredTexture2. Delete the default layer.
4. layeredTexture1 to the Alpha attribute of its corresponding layer in layeredTexture2 to connect the alpha attributes.
5. Add the File node to the bottom of layeredTexture2.
6. Connect layeredTexture2 to your Render Target via the color and alpha attributes.
   

7. In the Render View, select Render Target > renderTarget1.
   TipThe button in the Render View toolbar should be locked for this workflow because you are only working with the compositing graph and not making a change to the scene. Unlocking the button causes all passes and layers that are upstream of the render target to be re-rendered, which unnecessarily increases rendering times in this case.
8. Click .

The Render Target is rendered as follows.